“The future is psychedelic,” declared Rick Doblin, founder of Lykos Therapeutics, at a conference on psychedelic drugs last year. Several studies, many of them funded by Lykos, had provided tantalising signs that pairing MDMA with talk therapy could dramatically reduce symptoms of post-traumatic stress disorder (PTSD). As a result, Doblin was one of many advocates touting the drug as key to revolutionising mental healthcare.

But just a year later,…